Hydraulic pressure device and actuating fluid therefor



Patented Sept. 14, 1948 HYDRAULIC PRESSURE DEVICE AND ACTUATIN G FLUID THEREFOR Frank J. Sowa, Cranford, N. J.

No Drawing. Application October 28, 1942, Serial No. 483,684

Claims. (01. 252-78) The invention relates in general to actuating fluids and in particular to actuating fluids comprising organo-silicon compounds and includes correlated improvements designed to enhance their characteristics and extend their fields of use.

The properties of an actuating fluid which are of most importance in determining its success in use are its viscosity, its pour point, and its surface tension and their relatively slight variation over a wide temperature range. Other characteristics which influence the qualitiesof an actuating fluid are the boiling point, freedom from corrosive impurities, particularly those which corrode metals and swell rubber, and resistance to water, i. e. freedom from hydrolysis under conditions of use. The viscosity index is the most important characteristic, since the uniformity of operation of the fluid will depend upon the uniformity of its viscosity under slight temperature changes. The surface tension of a fluid determines the facility with which it wets the bearing surfaces and tends to creep into the engaging surfaces when the mechanism is static. H wever. it is most important that the actuating fluid be one which shows a high resistance to hydrolysis under the conditions of use.

In modern warfare there are numerous mechanisms employed which utilize actuating fluids either as shock absorbers or as force applying means. Among the shock absorbing devices are those employed on airplane landing wheels, gun recoil mechanisms, and the like; and among the force-applying devices are turret rotating means on tanks, firing mechanism on naval and fleld guns, braking devices on aircraft and trucks, fluid drive means on staif cars, and the like; Many of 4 these devices are used in desert warfare where the arctic regions andin the sub-stratosphere where a temperatures as low as -40 F. are encountered.

Thus the actuating fluids used in modern war machines must be capable of operating effectively and substantially uniformly over an extremely wide range of temperature and under It is a general object of the invention to provlde an actuating fluid having a high viscosity index over a wide range of temperature, a low pour point, a high surface tension, a low ccemcient of friction, and a substantial oiliness.

It is another object to provide an actuating fluid having a low pour point," that is, one which remains fluid at low temperatures, and whichwill have a. relativelylow vapor pressure.

It is a further object to provide an actuating fluid which will be non-hydrolyzing and which will not corrode such metals as copper, cast iron and aluminum.

According to the present invention, there is provided an actuating fluid comprising a nonhydrolysable liquid organo-silicon compound having a boiling point above C.

The invention also includes the hydraulic pressure device which device comprises in its essentials a cylinder or chamber inclosing a piston and an actuating fluid contained in the cylinder or chamber which fluid transmits or checks a force applied to the piston. In the appended claims,

actuating fluids are liquid substituted silicanes which are non-hydrolyzable under the conditions of use. In general suitable compounds are those having the general formula RySiXz in which R is an organic radical derived from aliphatic, aromatic, alicyclic and heterocyclic compounds, either saturated or unsaturated, and in which X represents hydrogen, hydroiiyl, fluorine,

R or -OR, 11 is an integer having the value 1, 2 i

or 3 and z is an integer having the value 1, 2 or 3. It is to be understood that in all of these compounds the size of the organic radical Ror the number of such radicals is suflicient to produce such steric .hindrance as will prevent any hydrolysis of the compound under the conditions of use. fluorine the organic radical should contain five or more carbon atoms or the organic radical should bearomatic in order to inhibit hydrolysis by steric hindrance.

By way of illustrating but not by way of limit- For example, where the silicane contains 3 ing the invention, there will be given several examples of different classes of organo-silicon compounds which comprise the actuating fluid of the invention:

1. Organo-silicon oxides: (R SDO 2. Silicyl ethers: RySiO-R Di-silicyl ethers: R Si-O-SiRy Silicols: RySi-OH Organo silicon hydrides: RyS1-Hz Organo silicon fluorides: RysiFz Polymeric silicones:

8. Fluorine-substituted silicanes: FRySiXz The organo-silicon compounds used in the present invention are characterized by being liquid from temperatures substantially below C. to temperatures above 100 C. f

It is to be understood that the actuating fluid of the present invention may comprise the liquid non-hydrolysing organo-silicon compounds alone denounce orin admixture with non-hydrolysing and nonoxidizing animal, mineral or vegetable oils, in particular, lubricating mineral oils. Thus the liquid organo-silicon compounds may be diluted to change their viscosity or flow characteristics, with lubricating or non-lubricating oils as mentioned, or diluted with stable organic liquids having boiling points above 100 C. Any of a great many liquids will serve as diluents. In fact, any liquid which is miscible with the silicon compounds, which has a low viscosity and a relatively low' vapor pressure at operating temperatures, which does not cause an appreciable swelling of rubber, and which does not react with metals, may be used. Many organic solvents will meet these requirements. Alcohols, however, especially those containing four carbon atoms or more, have been found to be particularly satisfactory. Short chain alcohols, such as ethyl and methyl alcohol, are useful but, because of their low boiling points, tend to raise the vapor pressure of the fluid more than the long chain alcohols. Diaceton alcohol, fusel oil (a mixture of amyl alcohols) and dihydric alcohols such as the glycol VI. The fluid drive mechanism of an automobile is actuated by use of liquid tributyl fluoro silicane which does not hydrolyse under the conethers are among those used. Of the glycol ethers,

the mono-ethyl ether of ethylene glycol and the I which is a liquid exhibiting no tendency to hydrolyse under the conditions of use.

II. An hydraulic braking mechanism is actuated by means of a fluid comprising a tri-butyl silicol.

III. The fluid chamber of a shock absorber for the landing wheels o an airplane is filled with a mixture of 70 parts of tri-ethyl silicon oxide and 30 parts of Unwilt 35 made by the Standard Oil Co. of New Jersey, a hydrocarbon lubricant. The fluid has a high viscosity index, remaining fluid at temperatures from C. to 100 C.

IV. A gun recoil shock absorber is filled with triamyl fluoro-silicane which remains fluid from -45 C. to 150 C. and does not hydrolyse under such conditions of use.

V. Two thirds of the oil normally used in a ditions of use and remains fluid from '-30 F. to 250 F., the operating range.

VII. For the dash-pot fluid used on trucks there is employed a liquid consisting of monofluoroamyl diamyl fluorosilicane. Owing to the large size of the organic radicals in this compound, the hydrolysis thereof is prevented by steric hindrance.

It is to be understood that the actuating fluids of the invention are especially adapted for use in warfare devices, such as turret-rotating means for trucks, firing mechanisms for guns, bombbay door operating devices for aircraft and the like because of their relatively slight variation in properties over a wide temperature range. The present actuating fluids are further advantageous because they do not attack or corrode iron, aluminum, copper and their alloys, do not swell synthetic rubbers, and are generally neutral in reaction.

I claim:

1. 'A hydraulic ressure device comprising the combination of a fluid chamber and an actuating fluid in said chamber con'sisting essentially of a. silicone, the organic constituents of which consist essentially of alkyl radicals attached directly to the silicon atoms.

2. A hydraulic pressure device comprising the combination of a fluid chamber and'an actuating fluid of high viscosity index, low pour point, high surface tension, low coeflicient of friction, and

substantial oiliness in said chamber consisting essentially of a homogeneous mixture of an organic liquid having a boiling point above C. which is inert to metals and a silicone, the-organic constituents of which consist essentially of alkyl radicals attached directly to the silicon atoms.

3. In the method of operating a hydraulic pressure device in which pressure exerted, on one member within a fluid chamber is transmitted to another member through a homogeneous liquid medium, the improvement in which theliquid medium consists essentially of a silicone, the organic constituents of which consist essentially of alkyl radicals attached directly to the silicon atoms.

4. In the method of operating a hydraulic pressure device in which pressure exerted on one member within a fluid chamber is transmitted to another member through a homogeneous liquid medium, the improvement'in which the liquid medium is of high viscosity index, low pour point, high surface tension, low coeflicient of friction, and substantial oiliness and consists essentially of a homogeneous mixture of an organic liquid having a boiling oint above 100 C. which is inert to metals and a silicone, the organic con stituents of which consist essentially of alkyl radicals, attached directly to the silicon atoms.

5. Hydraulic apparatus comprising, in combination, a movable member and a liquid medium arranged in contact with said member, said liduid medium consisting of a liquid silicone.

FRANK J. SOWA.

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